Piston Slap: Adding EFI to a Tri-Five Chevrolet?

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Jack (OP)

Jack writes:

I have a four-door 1956 Chevy Bel Air with the original 265 V-8, Powerglide transmission, frame-off restored, and cruises nicely. It’s perfect for me, I bought it on the day of our 42nd anniversary. The only problem with mine is it’s harder to start than I like, and belches too many smelly fumes. Oh, and I get terrible fuel economy.

We took a couple with us to view a large outdoor nativity scene, there were cars lined up for almost a mile so it was slow going. I lowered the windows to view the sights and the heavy fumes from my exhaust were pretty bad. My question is if I should consider electronic fuel injection and, especially, which one to consider installing? I see some EFI units that aren’t much bigger than a carburetor. I wonder if they come with a nice looking cover/filter of their own and if the smaller units are just as good.

She’s a keeper so any suggestions would be appreciated.

Sajeev answers:

That’s a lovely car, and I completely understand why you want to make it better! That said, you should also consider ditching the Powerglide transmission for an overdrive unit (700R4, maybe even the 200R4) if highway fuel economy is really that important. Or get a more modern, electronically controlled overdrive transmission that uses the same computer as the EFI setup you wish to add to the engine. But we are getting ahead of ourselves, and transmission swaps are often best discussed with a local shop willing to do the work.

Now let’s get to the main event, the fuel-injected event. The problem is a fuel-injected small-block Chevy is still gonna belch smelly fumes in bumper-to-bumper traffic, just a little less than before. You’ll have to add a catalytic converter to eliminate that raw, unburned gas smell. Adding one is a great idea, too, as the EFI computer will optimize both emissions for the converter and performance for your left foot. I reckon a universal 2-inch in, 2-inch out catalytic convertor is good enough for your engine, and they retail for less than $100. If only adding EFI was so affordable!

Walker Universal Catalytic Convertor 15038
Walker Exhaust

That said, after my time with aftermarket EFI setups and speaking to several tuners and experts, I’d lean strongly toward Holley’s conversion kits. Holley seems to have the best technology, competitive prices, and a wealth of independent EFI tuners willing to help iron out any bugs that might come your way. Holley (and the others) all make EFI setups that are throttle-body injection, so they mimic a carburetor’s footprint. (Check out the mounting flange information here.) Even cooler, they will likely accept your factory air cleaner (or any aftermarket air cleaner you so choose) since the overall height is usually very close to your current carburetor.

Holley Sniper EFI
Holley Performance Products

So that’s the easy part, but which Holley kit should you get? There’s the Terminator EFI and Sniper EFI. The Terminator is better if you want to add a modern overdrive transmission (one that needs a computer to function) but I reckon the Sniper is better for a more period-correct vehicle like yours. No matter—just like a carburetor, you need to ensure you pick the right size EFI system for your engine’s needs. I assume the Stealth 4150 is ideal for your powertrain.

I would absolutely add a TH-400 overdrive transmission, an off-the-shelf catalytic convertor, and the Holley Sniper EFI. But don’t take my word for it, as the beauty of Piston Slap is that others chime in with better advice. What say you, Hagerty Community?

Have a question you’d like answered on Piston Slap? Send your queries to pistonslap@hagerty.com, and give us as much detail as possible so we can help! If you need an expedited resolution, make a post on the Hagerty Community!

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